Scraper for double pipe chillers



June 1939- R. c. FULLER SCRAPER FOR DOUBLE PIPE CHILLERS Filed Sept. 15, 1958 Patented June 27, 1939 UNITED STATES PATENT OFFICE SCRAPER FOR DOUBLE PIPE CI-IILLERS Application September 15, 1938, Serial No. 230,152

Claims.

ural tendency of which is to collect upon the walls of the conduit in an adherent sediment or scale. Now, in the interest of efiicient heat exchange, it is essential, not only to keep the inner walls of the conduits free from deposits of this nature, but also to maintain them in smooth and polished condition.

For this purpose, it is customary to mount driven scrapers in the straight pipe sections of the chiller with spring blades which revolve against the inner surface of the conduit dislodging the adherent matter and keeping the surface of the conduit polished. Perhaps the scrapers find their greatest work to do when starting up after long rest periods of the chiller within which periods the adherent matter has had time to become firmly and thickly attached to the walls of the conduit.

The scraper blades may in general be of two types, straight blades which extend in the longitudinal direction of the conduit, and spiral blades. Where the latter type of blades is used,

the conveying function is quite subordinate to the scraping function inasmuch as the liquid being treated is pumped through the chiller, the spiral disposition of the blades being rather for the purpose of meeting the adherent matter at an angle thus performing an inclined shearing cut.

Inasmuch as the straight pipe sections of the chiller may be quite long and therefore subject to some slight sagging, it is customary to make the 5 scraper in sections in somewhat loosely articulated alignment so that the scraper blades of all the sections throughout their entire length may make contact with the interior wall of the conduit.

The object of the present invention is to provide an improved support for the scraper blades so as to ensure a substantially uniform radial pressure of said blades against the wall of the surrounding conduit, irrespective of the resist- 55 ance ofiered by the adherent matter, to prevent undue wear of the surface of the conduit and to prevent chattering by which is meant a vibratory contacting of the blade edge with the wall of the conduit and which results in scoring or grooving of the surface of the conduit.

Other objects of the invention will appear as the following description of a preferred and practical embodiment thereof proceeds.

In the drawing which accompanies and forms a part of the following specification and throughout the several figures of which the same characters of reference have been employed to designate identical parts:

Figure 1 is a longitudinal section through a double pipe chiller employing a scraper embodying the principles of the present invention, part of the chiller being broken away;

Figure 2 is a perspective view of a section of the improved scraper of the present invention illustrating the use of straight blades;

Figure 3 is a section taken along the line 3-3 of Figure 1, the scraper blades contacting the inner surface of the chiller at points remote from a diametrical plane through the straight pipe section;

Figure 4 is a slightly modified form of the invention in which the scraper blade contacts the wall of the straight pipe section at opposite points in a diametrical plane; and

Figure 5 is a fragmentary View illustrating the employment of a spiral blade.

Referring now in detail to the several figures, the numeral I represents in general a double pipe chiller comprising straight pipe sections 2 and 3, each being provided with a jacket 4. Said pipe sections are connected serially by return bends 5 and 6-. Liquid to be chilled is driven through the sinuous conduit of the chiller by a pump, not shown, and a refrigerant is circulated within the jackets 4. Thus heat exchange takes place through the walls of the straight pipe sections 2 and 3.

Shafts 1 and 8 extend axially through the pipe sections 2 and 3 and through stufiing glands 9 on the return bends. Said shafts are driven by suitable means such as sprockets l0 and H externally of the return bends at one end of the chiller. Inasmuch as the straight pipe sections may be of great length as is indicated by the break l2 in Figure 1, said shafts may be divided into sections as shown, the sections being formed hollow at the ends as at 14 in Figure 2, the abutting hollow ends of adjacent sections fitting loosely over a coupling pin 15, Figure 1, and being secured to said pin by suitable means such as the bolts or rivets I6. The looseness of fit of the adjacent sections with respect to the coupling pin permits them to wobble a little and enables the entire shaft to conform to the straight pipe sections even though the latter may be somewhat out of rectilinear alignment. At intervals, the shafts 1 and 8 are supported co-axially of the straight pipe sections by means of spiders II, the legs of which fit the inner wall of the straight pipe sections with a sliding fit and which spiders may form coupling means for adjacent shaft sections, being provided with extensions I8 which telescope loosely into the adjacent shaft section and being pinned thereto.

So much as has been related up to this point is common to scrapers for double pipe chillers already known. The present invention relates to the means for supporting the scraper blades and to the appurtenant combination of elements directly affected thereby.

The scraper blades l9 and 20 are arranged in opposite groups or pairs, in general several groups of blades being carried by a shaft section, and in offset or staggered relation to one another. In Figures 2 and 3 it will be seen that each of the scraper blades l9 and 20 is secured by riveting or equivalent means to resilient arms 2i and 22 arranged on opposite sides of the shaft and parallel to a diametrical plane. At their opposite ends from the scraper blades, the resilient arms 2| and 22 are secured as by the rivets 24 to rigid brackets 25 and 26. These brackets are identical so one only will be described. It has an arcuate portion 21 which fits the curvature of the shaft section and is perforated to receive a bolt 28 by means of which bolt the brackets 25 and 26 of a pair are firmly secured to the shaft section. In Figure 3 the arms 2| and 22 are of such length that the blades l9 and 20 contact the inner surface 29 of the pipe section at points which are on the opposite side from the points of attachment of the arms with their rigid supports with respect to a diametrical plane intersecting said arm. The direction of rotation of the scraper is indicated by the arrow in Figure 3 from which it will be deduced that the action of the scraper blades against adherent matter is chisel-like inasmuch as the blades meet the surface 29 at an angle other than a right angle.

Referring to that form of the invention shown in Figure 4, it is structurally identical with that of Figure 3 excepting that the resilient arms 30 and 3! are so short that the blades 19 and 20 meet the surface 29 at opposite points in a diametrical plane and therefore at right angles to said surface. Both of these structures are within the purview of the present invention although it is probable that that shown in Figure 3 is to be preferred.

It will be understood with regard to the spring type scraper for double pipe chillers, generally, that the force or pressure of the blade against adherent matter on the inner surface of the straight pipe sections resolves itself into two components, one acting radially against said surface and the other acting circumferen-tially. Ordinarily, as one of these components increases the other decreases and this constant relationship between the two components is probably theoretically true of all spring type scrapers. However, in an old type of spring type scraper, there is an undue and sometimes objectionable increase in the radial pressure of the scraper blades against the inner siuface of the chiller conduit, under certain conditions of operation,

which leads to undue wear, to chattering and grooving or scoring of the surface of the conduit and to unsatisfactory operation of the chiller. The construction of the present invention minimizes this increase in radial pressure, renders the radial pressure substantially uniform under all conditions of resistance occasioned by the adherent matter, promotes smoothness of operation of the scraper blades, avoids undue wear and avoids the destructive chattering of the scraper blades against the surface of the chiller conduit.

Referring to Figure 3, the points of attachment of the resilient arms 2| and 22 with the rigid brackets 25 and 26, never move out closer to the circumference of the inner surface of the pipe section and consequently there is no increase through this cause, of the force component acting radially against the inner surface of the pipe section. This permits a greater component of said force to act circumferentially in dislodging the adherent matter. Because of the fact that the radial pressure of the scraper blades against the inner surface of the chiller conduit is not increased, there is less Wear of said surface and an absence of that objectionable chattering which causes scoring and grooving of said surface.

By suitably staggering successive pairs of the supports as shown in Figure 5, the same construction as is illustrated in Figures 3 and 4 may be employed with spiral type blades.

While I have in the above description defined what I believe to be a preferred and practical embodiment of the invention, it will be understood to those skilled in the art that the details of construction as shown and described are by way of example and not to be construed as necessarily limiting the scope of the invention as defined in the appended claims.

What I claim is:

1. Scraper for double pipe chillers comprising a shaft, a blade extending longitudinally of said shaft and spaced therefrom, a support for said blade comprising a rigid bracket secured to said shaft and being extended to a point between said i shaft and the path of revolution of the working edge of said blade, and a resilient arm secured adjacent one end to said extended end of said bracket, said arm extending in such direction that the free end trails with respect to the direction of rotation of said shaft said blade being secured to the free end portion of said arm and having its working edge directed outwardly.

2. Scraper for double pipe chillers comprising a shaft, a blade extending longitudinally of said shaft and spaced therefrom, a support for said blade comprising a rigid bracket secured to said shaft and being extended in an advance direction with respect to the direction of rotation of said shaft to a point between said shaft and the path of revolution of the working edge of said blade, and a resilient arm secured adjacent one end to said extended end of said bracket, said arm extending in the opposite direction to the direction of extension of said bracket, said blade being secured to the free end portion of said arm and having its working edge directed outwardly.

3. Scraper for double pipe chillers comprising a shaft, a blade extending longitudinally of said shaft and spaced therefrom, a support for said blade comprising a rigid bracket secured to said shaft and being extended in an advance direction with respect to the direction of rotation of said shaft to a point between said shaft and the path of revolution of the working edge of said blade, and a resilient arm secured adjacent one end to said extended end of said bracket, said arm extending in the opposite direction to the direction of extension of said bracket and having the major portion thereof lying parallel to but non-coincident with a diametrical plane through said shaft, the free end portion of said arm being deflected outwardly, said blade being secured to said deflected portion and having its Working edge directed outwardly.

4. Scraper for double pipe chillers comprising a shaft, and the following instrumentalities disposed about said shaft in positions of opposite symmetry with respect to a median diametrical plane through said shaft; blades extending longitudinally of said shaft and spaced therefrom, and a support for each blade comprising a rigid bracket secured to said shaft and being extended to a point between said shaft and the path of revolution of the Working edges of said blades, and a resilient arm secured adjacent one end to said extended end of said bracket, said arms extending in such direction that the free ends trail with respect to the direction of rotation of said shaft said blades being secured to the free end portions of said arms and having their Working edges directed outwardly.

5. Scraper for double pipe chillers comprising a shaft, and the following instrumentalities disposed about said shaft in positions of opposite symmetry with respect to a median diametrical plane through said shaft; blades extending 1ongitudinally of said shaft and spaced therefrom, and a support for each blade comprising a rigid bracket secured to said shaft and being extended to a point between said shaft and the path of revolution of the working edges of said blades, and a resilient arm secured adjacent one end to said extended end of said bracket, said arm extending in the opposite direction to said bracket, with the major portion of said arm lying parallel to but non-coincident with a diametrical plane through said shaft, the free end portion of said arm being deflected outwardly, said scraper blades being secured to said deflected portions of said arms and having their working edges directed outwardly.

RAYMOND C. FULLER. 

